For combat soldiers, law enforcement personnel, and others, who are exposed to potential dangerous situation, the ready availability of information is essential in all environmental conditions. A Night Vision Device (NVD) is an optical instrument for producing images in levels of light approaching total darkness. NVD usually refers to a complete unit, including an image intensifier tube, a protective and generally water-resistant housing, and a mounting system. Many NVDs also include sacrificial lenses, IR illuminators, and telescopic lenses.
Low-light imaging, near-infrared illumination and thermal imaging are the common methods for achieving Night Vision. The most common applications of night vision systems are situational awareness, target cueing, night driving or flying, night security and surveillance, wildlife observation, sleep lab monitoring and search and rescue.
Night vision goggles generally are required to operate over scene luminance levels ranging from less than 1e−6 (1.0*10−6) fc (foot-candles) to more than 1 fc; a range of at least six orders of magnitude. The night vision goggles collect light over a broad wavelength spectrum, typically 500 nm to 900 nm for GEN III tubes, then amplify and convert the scene with a monochrome green phosphor, generally peaked around 540 nm. The image created is then displayed to the eye at about 1 to 2 fL (foot-lamberts).
A clip-on thermal imager, which are designed, to convert IR scene energy to visible or near IR and inject/project that converted scene into a night vision goggle must do their work at luminance levels compatible with the native night vision goggle near IR scene (i.e. operate over a dynamic range of 1e+6 or greater). Organic Light Emitting Diode (OLED) displays are generally limited to a dynamic range of less than five orders of magnitude or 1e+5:1, defined here as the ratio of the highest luminance level to the lowest addressable linear gray level. Given the limitations of the display threshold (lowest ON value) and pixel noise (variation in luminance for a given ON value), larger dynamic ranges would typically be achieved by operating the display to higher brightness levels, but with negative consequences of high power consumption and fess display life time. Current display systems do not cover larger dynamic range with wide range of attenuation capabilities.
Decker, U.S. Pat. No. 5,380,204 discloses a night vision goggle aided flight simulation system and technique that allows a flight simulator operator wearing night vision goggles to view an approximate simulation of night vision goggle aided flight. A processor generates at least one look-up table of brightness values utilizing database sources including any selected options. A scene generation computer will then generate the scene image with the contrast based on values provided by the look-up table. An image display system displays the scene at light levels with sufficient dynamic range so that approximate simulation of night vision goggle aided flight is achieved. A neutral density filter can be placed over a CRT display if the CRT display as the display system cannot produce sufficient dynamic range.
Whitehead et al., U.S. Pat. No. 7,801,426 discloses a display having a screen which incorporates a light modulator. The screen may be a front projection screen or a rear-projection screen. Elements of the light modulator may be controlled to adjust the intensity of light emanating from corresponding areas on the screen. The display may provide a high dynamic range.
Ben-Dravid et al., U.S. Pat. No. 8,248,440 discloses a color Liquid Crystal display (LCD) device for displaying a color image using at least four different primary colors, the device including as array of Liquid Crystal (LC) elements, driving circuitry adapted to receive an input corresponding to the color image and to selectively activate the LC elements of the LC array to produce an attenuation pattern corresponding to a gray-level representation of the color image, and an array of color sub-pixel filter elements juxtaposed and in registry with the array of LC elements such that each color sub-pixel filter element is in registry with one of the LC elements, wherein the array of color sub-pixel filter elements comprises at least four types of color sub-pixel filter elements, which transmit light of the at least four primary colors, respectively.
Ciurea, U.S. Pat. Application No. 20070242141 discloses an apparatus and method that extend the graduated neutral density filter approach by implementing an in-camera adjustable neutral density filter. The adjustable neutral density filter is implemented by the means of a transmissive LCD. The transmissive LCD is controlled to form a mask image. This mask image is able to be computed using an acquired signal wherein the acquired signal is then inverted and blurred. in an embodiment, a splitter and an additional sensor are utilized to acquire a split signal and then modify the split signal for use as the mask image. The other split signal is filtered through the mask image and transmissive LCD. Images with a high dynamic range compression are ultimately captured.
Malka et al., U.S. Pat. Application No. 20090179826 discloses methods and systems for displaying an image on a display, for example, a liquid crystal display (LCD) having more than three different colored filters. The display may include a plurality of sub-pixels, each of the sub-pixels being aligned with a filter having a color selected from a set of more than three different colors, none of which is white. A number of methods and systems for processing data for display are disclosed, for example, using data points from adjacent pixel groups, or data points for different colors within the same pixel data set.
A need therefore exists for display that covers a dynamic range greater than 1:105. A need also exists for the ability to attenuate brightness (amplitude) to match average scene brightness.